//
// SmoothScroll for websites v1.4.0 (Balazs Galambosi)
// http://www.smoothscroll.net/
//
// Licensed under the terms of the MIT license.
//
// You may use it in your theme if you credit me.
// It is also free to use on any individual website.
//
// Exception:
// The only restriction is to not publish any
// extension for browsers or native application
// without getting a written permission first.
//

(function () {

// Scroll Variables (tweakable)
  var defaultOptions = {

    // Scrolling Core
    frameRate        : 150, // [Hz]
    animationTime    : 400, // [ms]
    stepSize         : 100, // [px]

    // Pulse (less tweakable)
    // ratio of "tail" to "acceleration"
    pulseAlgorithm   : true,
    pulseScale       : 4,
    pulseNormalize   : 1,

    // Acceleration
    accelerationDelta : 50,  // 50
    accelerationMax   : 3,   // 3

    // Keyboard Settings
    keyboardSupport   : true,  // option
    arrowScroll       : 50,    // [px]

    // Other
    touchpadSupport   : false, // ignore touchpad by default
    fixedBackground   : true,
    excluded          : ''
  };

  var options = defaultOptions;


// Other Variables
  var isExcluded = false;
  var isFrame = false;
  var direction = { x: 0, y: 0 };
  var initDone  = false;
  var root = document.documentElement;
  var activeElement;
  var observer;
  var refreshSize;
  var deltaBuffer = [];
  var isMac = /^Mac/.test(navigator.platform);

  var key = { left: 37, up: 38, right: 39, down: 40, spacebar: 32,
    pageup: 33, pagedown: 34, end: 35, home: 36 };


  /***********************************************
   * INITIALIZE
   ***********************************************/

  /**
   * Tests if smooth scrolling is allowed. Shuts down everything if not.
   */
  function initTest() {
    if (options.keyboardSupport) {
      addEvent('keydown', keydown);
    }
  }

  /**
   * Sets up scrolls array, determines if frames are involved.
   */
  function init() {

    if (initDone || !document.body) return;

    initDone = true;

    var body = document.body;
    var html = document.documentElement;
    var windowHeight = window.innerHeight;
    var scrollHeight = body.scrollHeight;

    // check compat mode for root element
    root = (document.compatMode.indexOf('CSS') >= 0) ? html : body;
    activeElement = body;

    initTest();

    // Checks if this script is running in a frame
    if (top != self) {
      isFrame = true;
    }

    /**
     * Please duplicate this radar for a Safari fix!
     * rdar://22376037
     * https://openradar.appspot.com/radar?id=4965070979203072
     *
     * Only applies to Safari now, Chrome fixed it in v45:
     * This fixes a bug where the areas left and right to
     * the content does not trigger the onmousewheel event
     * on some pages. e.g.: html, body { height: 100% }
     */
    else if (scrollHeight > windowHeight &&
        (body.offsetHeight <= windowHeight ||
        html.offsetHeight <= windowHeight)) {

      var fullPageElem = document.createElement('div');
      fullPageElem.style.cssText = 'position:absolute; z-index:-10000; ' +
          'top:0; left:0; right:0; height:' +
          root.scrollHeight + 'px';
      document.body.appendChild(fullPageElem);

      // DOM changed (throttled) to fix height
      var pendingRefresh;
      refreshSize = function () {
        if (pendingRefresh) return; // could also be: clearTimeout(pendingRefresh);
        pendingRefresh = setTimeout(function () {
          if (isExcluded) return; // could be running after cleanup
          fullPageElem.style.height = '0';
          fullPageElem.style.height = root.scrollHeight + 'px';
          pendingRefresh = null;
        }, 500); // act rarely to stay fast
      };

      setTimeout(refreshSize, 10);

      addEvent('resize', refreshSize);

      // TODO: attributeFilter?
      var config = {
        attributes: true,
        childList: true,
        characterData: false
        // subtree: true
      };

      observer = new MutationObserver(refreshSize);
      observer.observe(body, config);

      if (root.offsetHeight <= windowHeight) {
        var clearfix = document.createElement('div');
        clearfix.style.clear = 'both';
        body.appendChild(clearfix);
      }
    }

    // disable fixed background
    if (!options.fixedBackground && !isExcluded) {
      body.style.backgroundAttachment = 'scroll';
      html.style.backgroundAttachment = 'scroll';
    }
  }

  /**
   * Removes event listeners and other traces left on the page.
   */
  function cleanup() {
    observer && observer.disconnect();
    removeEvent(wheelEvent, wheel);
    removeEvent('mousedown', mousedown);
    removeEvent('keydown', keydown);
    removeEvent('resize', refreshSize);
    removeEvent('load', init);
  }


  /************************************************
   * SCROLLING
   ************************************************/

  var que = [];
  var pending = false;
  var lastScroll = Date.now();

  /**
   * Pushes scroll actions to the scrolling queue.
   */
  function scrollArray(elem, left, top) {

    directionCheck(left, top);

    if (options.accelerationMax != 1) {
      var now = Date.now();
      var elapsed = now - lastScroll;
      if (elapsed < options.accelerationDelta) {
        var factor = (1 + (50 / elapsed)) / 2;
        if (factor > 1) {
          factor = Math.min(factor, options.accelerationMax);
          left *= factor;
          top  *= factor;
        }
      }
      lastScroll = Date.now();
    }

    // push a scroll command
    que.push({
      x: left,
      y: top,
      lastX: (left < 0) ? 0.99 : -0.99,
      lastY: (top  < 0) ? 0.99 : -0.99,
      start: Date.now()
    });

    // don't act if there's a pending queue
    if (pending) {
      return;
    }

    var scrollWindow = (elem === document.body);

    var step = function (time) {

      var now = Date.now();
      var scrollX = 0;
      var scrollY = 0;

      for (var i = 0; i < que.length; i++) {

        var item = que[i];
        var elapsed  = now - item.start;
        var finished = (elapsed >= options.animationTime);

        // scroll position: [0, 1]
        var position = (finished) ? 1 : elapsed / options.animationTime;

        // easing [optional]
        if (options.pulseAlgorithm) {
          position = pulse(position);
        }

        // only need the difference
        var x = (item.x * position - item.lastX) >> 0;
        var y = (item.y * position - item.lastY) >> 0;

        // add this to the total scrolling
        scrollX += x;
        scrollY += y;

        // update last values
        item.lastX += x;
        item.lastY += y;

        // delete and step back if it's over
        if (finished) {
          que.splice(i, 1); i--;
        }
      }

      // scroll left and top
      if (scrollWindow) {
        window.scrollBy(scrollX, scrollY);
      }
      else {
        if (scrollX) elem.scrollLeft += scrollX;
        if (scrollY) elem.scrollTop  += scrollY;
      }

      // clean up if there's nothing left to do
      if (!left && !top) {
        que = [];
      }

      if (que.length) {
        requestFrame(step, elem, (1000 / options.frameRate + 1));
      } else {
        pending = false;
      }
    };

    // start a new queue of actions
    requestFrame(step, elem, 0);
    pending = true;
  }


  /***********************************************
   * EVENTS
   ***********************************************/

  /**
   * Mouse wheel handler.
   * @param {Object} event
   */
  function wheel(event) {

    if (!initDone) {
      init();
    }

    var target = event.target;
    var overflowing = overflowingAncestor(target);

    // use default if there's no overflowing
    // element or default action is prevented
    // or it's a zooming event with CTRL
    if (!overflowing || event.defaultPrevented || event.ctrlKey) {
      return true;
    }

    // leave embedded content alone (flash & pdf)
    if (isNodeName(activeElement, 'embed') ||
        (isNodeName(target, 'embed') && /\.pdf/i.test(target.src)) ||
        isNodeName(activeElement, 'object')) {
      return true;
    }

    var deltaX = -event.wheelDeltaX || event.deltaX || 0;
    var deltaY = -event.wheelDeltaY || event.deltaY || 0;

    if (isMac) {
      if (event.wheelDeltaX && isDivisible(event.wheelDeltaX, 120)) {
        deltaX = -120 * (event.wheelDeltaX / Math.abs(event.wheelDeltaX));
      }
      if (event.wheelDeltaY && isDivisible(event.wheelDeltaY, 120)) {
        deltaY = -120 * (event.wheelDeltaY / Math.abs(event.wheelDeltaY));
      }
    }

    // use wheelDelta if deltaX/Y is not available
    if (!deltaX && !deltaY) {
      deltaY = -event.wheelDelta || 0;
    }

    // line based scrolling (Firefox mostly)
    if (event.deltaMode === 1) {
      deltaX *= 40;
      deltaY *= 40;
    }

    // check if it's a touchpad scroll that should be ignored
    if (!options.touchpadSupport && isTouchpad(deltaY)) {
      return true;
    }

    // scale by step size
    // delta is 120 most of the time
    // synaptics seems to send 1 sometimes
    if (Math.abs(deltaX) > 1.2) {
      deltaX *= options.stepSize / 120;
    }
    if (Math.abs(deltaY) > 1.2) {
      deltaY *= options.stepSize / 120;
    }

    scrollArray(overflowing, deltaX, deltaY);
    event.preventDefault();
    scheduleClearCache();
  }

  /**
   * Keydown event handler.
   * @param {Object} event
   */
  function keydown(event) {

    var target   = event.target;
    var modifier = event.ctrlKey || event.altKey || event.metaKey ||
        (event.shiftKey && event.keyCode !== key.spacebar);

    // our own tracked active element could've been removed from the DOM
    if (!document.contains(activeElement)) {
      activeElement = document.activeElement;
    }

    // do nothing if user is editing text
    // or using a modifier key (except shift)
    // or in a dropdown
    // or inside interactive elements
    var inputNodeNames = /^(textarea|select|embed|object)$/i;
    var buttonTypes = /^(button|submit|radio|checkbox|file|color|image)$/i;
    if ( inputNodeNames.test(target.nodeName) ||
        isNodeName(target, 'input') && !buttonTypes.test(target.type) ||
        isNodeName(activeElement, 'video') ||
        isInsideYoutubeVideo(event) ||
        target.isContentEditable ||
        event.defaultPrevented   ||
        modifier ) {
      return true;
    }

    // spacebar should trigger button press
    if ((isNodeName(target, 'button') ||
        isNodeName(target, 'input') && buttonTypes.test(target.type)) &&
        event.keyCode === key.spacebar) {
      return true;
    }

    var shift, x = 0, y = 0;
    var elem = overflowingAncestor(activeElement);
    var clientHeight = elem.clientHeight;

    if (elem == document.body) {
      clientHeight = window.innerHeight;
    }

    switch (event.keyCode) {
      case key.up:
        y = -options.arrowScroll;
        break;
      case key.down:
        y = options.arrowScroll;
        break;
      case key.spacebar: // (+ shift)
        shift = event.shiftKey ? 1 : -1;
        y = -shift * clientHeight * 0.9;
        break;
      case key.pageup:
        y = -clientHeight * 0.9;
        break;
      case key.pagedown:
        y = clientHeight * 0.9;
        break;
      case key.home:
        y = -elem.scrollTop;
        break;
      case key.end:
        var damt = elem.scrollHeight - elem.scrollTop - clientHeight;
        y = (damt > 0) ? damt+10 : 0;
        break;
      case key.left:
        x = -options.arrowScroll;
        break;
      case key.right:
        x = options.arrowScroll;
        break;
      default:
        return true; // a key we don't care about
    }

    scrollArray(elem, x, y);
    event.preventDefault();
    scheduleClearCache();
  }

  /**
   * Mousedown event only for updating activeElement
   */
  function mousedown(event) {
    activeElement = event.target;
  }


  /***********************************************
   * OVERFLOW
   ***********************************************/

  var uniqueID = (function () {
    var i = 0;
    return function (el) {
      return el.uniqueID || (el.uniqueID = i++);
    };
  })();

  var cache = {}; // cleared out after a scrolling session
  var clearCacheTimer;

//setInterval(function () { cache = {}; }, 10 * 1000);

  function scheduleClearCache() {
    clearTimeout(clearCacheTimer);
    clearCacheTimer = setInterval(function () { cache = {}; }, 1*1000);
  }

  function setCache(elems, overflowing) {
    for (var i = elems.length; i--;)
      cache[uniqueID(elems[i])] = overflowing;
    return overflowing;
  }

//  (body)                (root)
//         | hidden | visible | scroll |  auto  |
// hidden  |   no   |    no   |   YES  |   YES  |
// visible |   no   |   YES   |   YES  |   YES  |
// scroll  |   no   |   YES   |   YES  |   YES  |
// auto    |   no   |   YES   |   YES  |   YES  |

  function overflowingAncestor(el) {
    var elems = [];
    var body = document.body;
    var rootScrollHeight = root.scrollHeight;
    do {
      var cached = cache[uniqueID(el)];
      if (cached) {
        return setCache(elems, cached);
      }
      elems.push(el);
      if (rootScrollHeight === el.scrollHeight) {
        var topOverflowsNotHidden = overflowNotHidden(root) && overflowNotHidden(body);
        var isOverflowCSS = topOverflowsNotHidden || overflowAutoOrScroll(root);
        if (isFrame && isContentOverflowing(root) ||
            !isFrame && isOverflowCSS) {
          return setCache(elems, getScrollRoot());
        }
      } else if (isContentOverflowing(el) && overflowAutoOrScroll(el)) {
        return setCache(elems, el);
      }
    } while (el = el.parentElement);
  }

  function isContentOverflowing(el) {
    return (el.clientHeight + 10 < el.scrollHeight);
  }

// typically for <body> and <html>
  function overflowNotHidden(el) {
    var overflow = getComputedStyle(el, '').getPropertyValue('overflow-y');
    return (overflow !== 'hidden');
  }

// for all other elements
  function overflowAutoOrScroll(el) {
    var overflow = getComputedStyle(el, '').getPropertyValue('overflow-y');
    return (overflow === 'scroll' || overflow === 'auto');
  }


  /***********************************************
   * HELPERS
   ***********************************************/

  function addEvent(type, fn) {
    window.addEventListener(type, fn, false);
  }

  function removeEvent(type, fn) {
    window.removeEventListener(type, fn, false);
  }

  function isNodeName(el, tag) {
    return (el.nodeName||'').toLowerCase() === tag.toLowerCase();
  }

  function directionCheck(x, y) {
    x = (x > 0) ? 1 : -1;
    y = (y > 0) ? 1 : -1;
    if (direction.x !== x || direction.y !== y) {
      direction.x = x;
      direction.y = y;
      que = [];
      lastScroll = 0;
    }
  }

  var deltaBufferTimer;

  if (window.localStorage && localStorage.SS_deltaBuffer) {
    deltaBuffer = localStorage.SS_deltaBuffer.split(',');
  }

  function isTouchpad(deltaY) {
    if (!deltaY) return;
    if (!deltaBuffer.length) {
      deltaBuffer = [deltaY, deltaY, deltaY];
    }
    deltaY = Math.abs(deltaY)
    deltaBuffer.push(deltaY);
    deltaBuffer.shift();
    clearTimeout(deltaBufferTimer);
    deltaBufferTimer = setTimeout(function () {
      if (window.localStorage) {
        localStorage.SS_deltaBuffer = deltaBuffer.join(',');
      }
    }, 1000);
    return !allDeltasDivisableBy(120) && !allDeltasDivisableBy(100);
  }

  function isDivisible(n, divisor) {
    return (Math.floor(n / divisor) == n / divisor);
  }

  function allDeltasDivisableBy(divisor) {
    return (isDivisible(deltaBuffer[0], divisor) &&
    isDivisible(deltaBuffer[1], divisor) &&
    isDivisible(deltaBuffer[2], divisor));
  }

  function isInsideYoutubeVideo(event) {
    var elem = event.target;
    var isControl = false;
    if (document.URL.indexOf ('www.youtube.com/watch') != -1) {
      do {
        isControl = (elem.classList &&
        elem.classList.contains('html5-video-controls'));
        if (isControl) break;
      } while (elem = elem.parentNode);
    }
    return isControl;
  }

  var requestFrame = (function () {
    return (window.requestAnimationFrame       ||
    window.webkitRequestAnimationFrame ||
    window.mozRequestAnimationFrame    ||
    function (callback, element, delay) {
      window.setTimeout(callback, delay || (1000/60));
    });
  })();

  var MutationObserver = (window.MutationObserver ||
  window.WebKitMutationObserver ||
  window.MozMutationObserver);

  var getScrollRoot = (function() {
    var SCROLL_ROOT;
    return function() {
      if (!SCROLL_ROOT) {
        var dummy = document.createElement('div');
        dummy.style.cssText = 'height:10000px;width:1px;';
        document.body.appendChild(dummy);
        var bodyScrollTop  = document.body.scrollTop;
        var docElScrollTop = document.documentElement.scrollTop;
        window.scrollBy(0, 3);
        if (document.body.scrollTop != bodyScrollTop)
          (SCROLL_ROOT = document.body);
        else
          (SCROLL_ROOT = document.documentElement);
        window.scrollBy(0, -3);
        document.body.removeChild(dummy);
      }
      return SCROLL_ROOT;
    };
  })();


  /***********************************************
   * PULSE (by Michael Herf)
   ***********************************************/

  /**
   * Viscous fluid with a pulse for part and decay for the rest.
   * - Applies a fixed force over an interval (a damped acceleration), and
   * - Lets the exponential bleed away the velocity over a longer interval
   * - Michael Herf, http://stereopsis.com/stopping/
   */
  function pulse_(x) {
    var val, start, expx;
    // test
    x = x * options.pulseScale;
    if (x < 1) { // acceleartion
      val = x - (1 - Math.exp(-x));
    } else {     // tail
      // the previous animation ended here:
      start = Math.exp(-1);
      // simple viscous drag
      x -= 1;
      expx = 1 - Math.exp(-x);
      val = start + (expx * (1 - start));
    }
    return val * options.pulseNormalize;
  }

  function pulse(x) {
    if (x >= 1) return 1;
    if (x <= 0) return 0;

    if (options.pulseNormalize == 1) {
      options.pulseNormalize /= pulse_(1);
    }
    return pulse_(x);
  }


  /***********************************************
   * FIRST RUN
   ***********************************************/

  var userAgent = window.navigator.userAgent;
  var isEdge    = /Edge/.test(userAgent); // thank you MS
  var isChrome  = /chrome/i.test(userAgent) && !isEdge;
  var isSafari  = /safari/i.test(userAgent) && !isEdge;
  var isMobile  = /mobile/i.test(userAgent);
  var isEnabledForBrowser = (isChrome || isSafari) && !isMobile;

  var wheelEvent;
  if ('onwheel' in document.createElement('div'))
    wheelEvent = 'wheel';
  else if ('onmousewheel' in document.createElement('div'))
    wheelEvent = 'mousewheel';

  if (wheelEvent && isEnabledForBrowser) {
    addEvent(wheelEvent, wheel);
    addEvent('mousedown', mousedown);
    addEvent('load', init);
  }


  /***********************************************
   * PUBLIC INTERFACE
   ***********************************************/

  function SmoothScroll(optionsToSet) {
    for (var key in optionsToSet)
      if (defaultOptions.hasOwnProperty(key))
        options[key] = optionsToSet[key];
  }
  SmoothScroll.destroy = cleanup;

  if (window.SmoothScrollOptions) // async API
    SmoothScroll(window.SmoothScrollOptions)

  if (typeof define === 'function' && define.amd)
    define(function() {
      return SmoothScroll;
    });
  else if ('object' == typeof exports)
    module.exports = SmoothScroll;
  else
    window.SmoothScroll = SmoothScroll;

})();
